1. Technical Field
The present invention relates to a vehicle safety apparatus and, in particular, to an inflator for an inflatable vehicle occupant protection device, such as an air bag.
2. Description of the Prior Art
It is known to inflate a vehicle occupant protection device, such as an air bag, to help protect a vehicle occupant. The air bag is inflated by inflation fluid from an inflator.
Some air bag inflators include inflation fluid stored under pressure in a chamber in a container. A burst disk blocks flow of inflation fluid from the chamber. An initiator is actuatable to rupture the burst disk and to initiate flow of inflation fluid from the chamber to inflate the air bag. One type of inflator includes a pyrotechnic material which, when ignited, generates combustion products for heating and pressurizing the inflation fluid stored in the chamber.
It is known to tailor the output pressure of an inflator, in order to inflate an air bag in a predetermined manner over a period of time. For example, it is known to begin inflating an air bag at first with inflation fluid at a relatively low pressure, then finish inflating the air bag with inflation fluid at a relatively high pressure. Some known inflators of this type have two independently actuatable pyrotechnic charges for heating and pressurizing inflation fluid stored in a container.